When your blood sugar is high, the most important first steps are drinking water, checking for ketones if you’re above 240 mg/dL, and avoiding exercise until you know your ketone status. Most mild to moderate spikes can be managed at home with hydration, the right foods, and medication adjustments if you’re on insulin. But readings above 300 mg/dL or symptoms like vomiting and fruity-smelling breath require emergency care.
Know Your Numbers First
Not all high blood sugar readings carry the same urgency. A reading of 180 mg/dL after a big meal is different from a fasting reading of 300 mg/dL. Your target range depends on your individual plan, but general thresholds help you decide what to do next.
At 240 mg/dL or above, the CDC recommends using an over-the-counter ketone test kit. High ketones are an early sign of diabetic ketoacidosis (DKA), a dangerous condition where the body starts breaking down fat for energy because it can’t use glucose properly. At 300 mg/dL or above, especially with symptoms, you should go to the emergency room or call 911. The same applies if your breath smells fruity, you’re vomiting and can’t keep fluids down, or you’re having trouble breathing.
Drink Water Right Away
Water is your simplest and most immediate tool. When blood sugar is elevated, your kidneys try to flush the excess glucose through urine. That process pulls water along with it, which is why high blood sugar makes you urinate more frequently and feel intensely thirsty. Drinking water supports your kidneys in clearing that extra glucose and helps prevent the dehydration that high blood sugar causes on its own.
Plain water is the best choice. Avoid juice, soda, or sports drinks with added sugar. If you find plain water hard to drink in large amounts, sparkling water or water with a squeeze of lemon works fine. Aim to sip steadily rather than forcing yourself to drink a huge amount at once.
Check for Ketones Before You Exercise
Your instinct might be to go for a walk or hit the gym, and light physical activity can help lower blood sugar in many situations. But there’s an important exception. If your body doesn’t have enough insulin available, exercise can actually make things worse by triggering your liver to release even more glucose and pushing you toward ketoacidosis.
Before exercising with high blood sugar, test your urine for ketones. Ketone test strips are available at most pharmacies without a prescription. You either hold the strip in your urine stream or dip it into a collected sample, then compare the color change to the chart on the package. If ketones are present, skip exercise entirely. Take steps to lower your blood sugar first, and wait until a follow-up test shows no ketones before working out.
If your ketone test is negative and your blood sugar is elevated but not in the danger zone, a 15 to 30 minute walk can help your muscles pull glucose from the bloodstream and bring your numbers down.
Adjust Your Medication If You Have a Plan
If you take insulin, you may have a correction dose built into your diabetes management plan. This is a specific amount of rapid-acting insulin calculated to bring a high reading back into range. Your correction factor tells you how much one unit of insulin will lower your blood sugar, and it’s unique to you based on your total daily insulin needs.
If your doctor has given you a correction plan, follow it. If you don’t have one, or you’re unsure how much insulin to take, call your care team before making changes. Taking too much insulin to “fix” a high reading can swing you into dangerously low blood sugar, which brings its own set of risks. Never double up on doses or guess at corrections without guidance.
For people on oral diabetes medications rather than insulin, there typically isn’t a quick-acting correction option. Your medication works on a longer timeline, so hydration, food choices, and activity become your main tools in the short term.
Eat to Stabilize, Not to Spike
When your blood sugar is already high, what you eat next matters. This isn’t the time for white bread, rice, or sugary snacks. Instead, focus on foods that are high in fiber, protein, and healthy fats, which slow digestion and prevent further spikes.
- Beans and lentils are packed with fiber and plant-based protein. A half cup provides as much protein as an ounce of meat without the saturated fat.
- Nuts like walnuts or almonds offer healthy fats, magnesium, and fiber, and help manage hunger between meals.
- Dark leafy greens such as spinach and kale are very low in carbohydrates and calories while providing vitamins A, C, and K.
- Avocado contributes heart-healthy fat and fiber that help you feel full without pushing glucose higher.
- Berries satisfy a sweet craving while delivering fiber and antioxidants with a lower sugar load than tropical fruits or juice.
A practical combination: plain Greek yogurt topped with berries and a handful of walnuts. The protein from the yogurt, fiber from the berries, and fat from the nuts work together to keep your blood sugar steadier than any single food would on its own.
Figure Out What Caused the Spike
A single high reading is worth managing. Repeated highs are worth investigating. Several factors beyond food can push blood sugar up, and identifying the trigger helps you prevent the next spike.
Illness and infection are common culprits. When your body fights off a cold, flu, or even a urinary tract infection, it releases stress hormones that raise blood sugar. Emotional stress does the same thing: family conflict, work pressure, and poor sleep all trigger hormonal responses that make your cells less responsive to insulin. Some medications, particularly steroids and immunosuppressants, can also raise blood sugar significantly.
Other practical causes include skipping or mistiming diabetes medication, using insulin that wasn’t stored properly and has expired, injecting insulin incorrectly, or simply being less physically active than usual. Even a week of reduced movement, like recovering from an injury or sitting through long travel days, can shift your numbers upward.
Recognize Warning Signs That Need Emergency Care
Most high blood sugar episodes resolve with the steps above. But DKA can develop quickly if insulin levels are too low, particularly in people with type 1 diabetes. Early symptoms are easy to dismiss: increased thirst and frequent urination. If those go unaddressed, more severe signs can follow rapidly.
Watch for fast, deep breathing, dry skin and mouth, a flushed face, fruity-smelling breath, nausea or vomiting, stomach pain, muscle stiffness, severe fatigue, or headache. If you experience multiple symptoms together, or your blood sugar stays at or above 300 mg/dL and won’t come down, get emergency care. Vomiting is especially concerning because it prevents you from staying hydrated or keeping oral medications down, which accelerates the problem.
Build Habits That Prevent Future Spikes
Managing a spike in the moment is one thing. Reducing how often spikes happen is where the real payoff lies. Consistent meal timing, regular physical activity, and a diet built around fiber, protein, and healthy fats form the foundation. Whole grains like oats, quinoa, and barley are better choices than refined grains because they digest more slowly and produce a gentler blood sugar curve.
Magnesium intake also plays a role. A meta-analysis of eighteen clinical trials found that people with type 2 diabetes who supplemented with magnesium saw meaningful improvements in fasting blood sugar and long-term glucose control (measured by HbA1c) over 24 weeks. The estimated drop in fasting blood sugar was about 15 mg/dL. Foods rich in magnesium include nuts, leafy greens, beans, and whole grains, many of the same foods that help stabilize blood sugar through fiber and protein. If your diet is low in these foods, supplementation is worth discussing with your care team.
Keeping ketone test strips and a reliable glucose meter at home means you’re prepared when a spike happens. Knowing your personal correction plan, your trigger patterns, and your emergency thresholds turns a stressful moment into one you can handle with confidence.